Oriented PZT Thin Films Research Articles

Multi-step switchable superdomain architecture with enhanced photoelectrical performance in epitaxial ferroelectrics

Ferroic domains and relevant topological defects, such as domain walls and vortices, have gained significant attention as functional units for potential advancements in nanoelectronics. Pb(ZrxTi1-x)O3 (PZT) is a tetragonal ferroelectric material at room-temperature, exhibiting remarkable piezoelectricity and intricate domain structures. In this work, we explore the ferroelectric properties, photoelectric reactions, and efficient manipulation pathways of the unconventional superstructures in epitaxial (101)-oriented PZT thin films. Employing piezoresponse force microscopy (PFM) and conductive atomic force microscopy (cAFM), we unveil the three-dimensional polarization configurations of the superdomain structures inherently featuring conductive charged domain walls. Our findings reveal an increase in photoactivity at the head-side charged domain walls, attributed to the band-bending mechanism. Additionally, we discover the enhanced photoelectrochemical (PEC) performance in the superdomain structures compared to the (101)-oriented PZT films with conventional c/a domains. Furthermore, time-dependent pulse voltages are utilized to dynamically assess local currents and realize direct conductivity modulation by manipulating distinct polarization states. The elucidation of the photoelectrical mechanism and delineation of diverse pathways for intermediate state control underscore the potential of ferroelectric superdomains in constructing functional photoelectronic nanodevices.

Enhanced electrical and fatigue properties of La-modified (100)-oriented PZT thin films with various Zr/Ti ratio

Pb1−x(LaxZryTi1−y)O3 (PLZT) (x = 0%, 2%, 4%; y = 0.45, 0.52, 0.60) thin films were fabricated by sol–gel process to investigate the effects of La-doped and Zr/Ti ratio on crystalline orientation, microstructure, and electrical properties of lead zirconate titanate films. The results of X-ray diffraction analysis showed that the orientation of the films with various La concentration change with the Zr/Ti ratio. The Zr-rich composition (y = 0.60) with the fixed 2% La doping concentration has the most (100) preferential orientation. Scanning electron microscope analysis showed that the films exhibit dense perovskite structure when the doping concentration was less than 4%. The maximum dielectric constant (1364.65 at 100 Hz), optimized ferroelectric properties, and a low leakage current density of 8.63 × 10−8 A cm−2 were obtained for 2% La-doped film with a Zr/Ti ratio of 60/40. The lowest value of coercive field (Ec) was generated in the film fabricated with a Zr/Ti ratio of 52/48 when the La doping concentration was 2%. Fatigue resistance was also improved with 2% La dopant for the films processed by a Zr/Ti ratio of 52/48 and 60/40.

Characterizations of Pb(Zr0.52Ti0.48)O3 thin film processed for sensor and actuator applications

This paper describes the process and characterization of lead zirconate titanate (PZT) for sensors and actuators applications. The influence of substrate texture and properties along with the heat treatment process on the film crystallization mechanism is discussed. During the process, the Platinum bottom electrode is deposited on silicon substrate by electron beam evaporation (e-beam) process, providing us with a high quality Platinum layer to control PZT thin film growth. The surface quality of Titanium/Platinum (Ti/Pt) layer is analyzed using atomic force microscope (AFM). An optimized heat treatment process is proposed to obtain dense, uniform and cracks free PZT thin films with a fully perovskite crystallographic structure. Depending on Ti/Pt heat treatment, preferential PZT orientations (100) and (111) are successfully obtained. The films morphology is analyzed using Scanning Electron Microscope (SEM) and the crystallographic structure is studied using x-ray diffraction (XRD) and Raman spectroscopy. MIM (metal-insulator-metal) structures with different dimensions are fabricated to evaluate electric characteristics and ferroelectric effect of the proposed PZT thin films. A variation of capacitance value is successfully observed according to the variation of frequency, DC bias voltage and MIM structure dimensions. The relative permittivity is then extracted depending on capacitances variations. We demonstrate therefore that the capacitance and the relative permittivity presents a higher value for (111) than (100) oriented PZT thin film. This comforts the fact that (111) orientation is better for ferroelectric applications.

Improved ferroelectric properties of (100)-oriented PZT thin films deposited on stainless steel substrates with La0.5Sr0.5CoO3 buffer layers

Ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT) thin films were deposited on La0.5Sr0.5CoO3 (LSCO) buffered stainless steel (SS) substrates by the sol–gel processes. The introduction of LSCO buffer layers facilitated the formation of (100)-oriented PZT thin films, and the (100) orientation degree of PZT thin films was obviously improved from 20 to 62%. Such PZT thin films with smooth and dense microstructures exhibited enhanced remnant polarization, reduced dielectric loss and leakage current density of 42 µC/cm2, 2.7% at 1 kHz, and 7.6 × 10− 7 A/cm2 at 300 kV/cm, respectively. Moreover, the fatigue endurance property of PZT thin films was also improved.

Energy storage characteristics of {001} oriented Pb(Zr0.52Ti0.48)O3 thin film grown by chemical solution deposition

Capacitors with high energy density and high discharging rate have been attracting attention for electric vehicles and military applications, in which the rapid discharge of large amounts of electric energy is required. Since ferroelectric thin film of perovskite structure has different polarization characteristics according to its crystallographic orientation, the charged energy density can be tailored. In this study, we investigated the effect of the crystallographic orientation of Pb(Zr0.52Ti0.48)O3 (PZT) thin films grown by chemical solution deposition on the energy storage capability and discharging rate. The {001} and randomly oriented PZT thin films were prepared and their dielectric and ferroelectric properties, stored energy densities, and discharging rates were characterized. The storage energy density of {001}-oriented film was found to be superior to that of other films, while its efficiency was nearly the same. It is believed that {001} oriented PZT thin film has potential for use in high performance capacitors with large energy density.

Fabrication and characterization of {110}-oriented Pb(Zr,Ti)O3 thin films on Pt/SiO2/Si substrates using PdO//Pd buffer layer

A strongly {110}-oriented perovskite-type thin film of tetragonal Pb(Zr0.4Ti0.6)O3 (PZT) was successfully obtained on a (100)Si substrate using a {101}PdO//{111}Pd thin film as a buffer layer. The {101}PdO//{111}Pd thin film buffer layer was obtained by oxidizing {111}Pd after depositing {111}Pd on a {111}Pt/TiOx/SiO2/{100}Si substrate. Using this buffer layer, a {110}c-oriented SrRuO3 (SRO) thin film was deposited by sputtering as a bottom electrode of PZT thin films. Subsequently, the {110}-oriented PZT thin film can be deposited on a (110)cSRO thin film by metal–organic chemical deposition (MOCVD) and its properties can be compared with those of PZT thin films with other orientations of {100} and {111}. Among the {100}, {110}, {111}-oriented PZT films, the {100}-oriented one showed the largest remnant polarization, which is in good agreement with those of the PZTs epitaxially grown in the 〈100〉, 〈110〉, and 〈111〉 directions. The other properties, i.e., piezoelectricity and dielectric constants, also showed similar anisotropic tendencies, which is in good agreement with the data reported in the epitaxially grown PZTs.

Optical and electro-optic anisotropy of epitaxial PZT thin films

Strong optical and electro-optic (EO) anisotropy has been investigated in ferroelectric Pb(Zr0.48Ti0.52)O3 thin films epitaxially grown on Nb-SrTiO3 (001), (011), and (111) substrates using magnetron sputtering. The refractive index, electro-optic, and ferroelectric properties of the samples demonstrate the significant dependence on the growth orientation. The linear electro-optic coefficients of the (001), (011), and (111)-oriented PZT thin films were 270.8, 198.8, and 125.7 pm/V, respectively. Such remarkable anisotropic EO behaviors have been explained according to the structure correlation between the orientation dependent distribution, spontaneous polarization, epitaxial strain, and domain pattern.

Fabrication and characterisation of lead zirconate titanate thin films for microactuators

Lead zirconate titanate (PZT) thin films have played an important role in the performance of microactuators. A description is provided of the effects of different heat treatment processes on the orientation and microstructures of PZT thin films deposited by the chemical solution deposition method. X-ray diffractometry and field-emission scanning electron microscopy were used to characterise the orientation and microstructures of the thin films. It was found that the intensity of the (100) peak weakens along with the increase of the pyrolytic layer thickness before 600°C annealing. Thin pyrolytic layers obtained highly (100)-oriented structures with distinct grain boundaries after 600°C annealing heat treatment. For comparison, membrane structures were fabricated to test the performance of PZT thin films with different orientations and different microstructures. The results show that highly (100)-oriented PZT thin film yields higher deformation and shows better dielectric properties.

Study of (111)-oriented PZT thin films prepared by a modified sol–gel method

In this paper, Pb(Zr0.52Ti0.48)O3 thin films were successfully deposited on platinized silicon substrates and silicon substrates with PbTiO3 seed layer by a modified sol–gel processing. The results show that the films were more likely to grow on platinum substrate, and the PbTiO3 seed layer promoted the grain growth and influenced the crystal orientation of the films. With the annealing temperature and sintering time rising (from 600 °C for 1 h to 700 °C for 2 h) in the new method, the crystal orientation of PZT deposited on Pt substrate with PbTiO3 seed layer changed from (100) to (111), and the grain size increased from dozens to hundreds of nanometer. Meanwhile, its ferroelectric and dielectric properties were greatly improved with 2Pr from 10.78 to 42.12 μC/cm2and er from 348 to 978, respectively.

Pb(Zr,Ti)O3 recording media for probe data storage devices prepared by rf magnetron sputtering

Pb(Zr,Ti)O3 (PZT) thin films for ferroelectric probe data storage technology were studied. (001)-oriented PZT thin films were deposited on SrRuO3/SrTiO3 substrates by rf magnetron sputtering. Dc voltage was applied on the films using a metal-coated tip and the poling region was observed by scanning nonlinear dielectric microscopy (SNDM). The contrasts in the positive and negative poling regions in the SNDM images obtained were improved by using the PZT films after ion-beam irradiation. This suggests that a surface layer of a few nanometers in thickness was formed on the as-grown PZT film and the polarization was not invertible in the surface layer. The deposition condition was examined with focus on deposition temperature. Nanosized domain dots were successfully formed on a PZT film deposited at 550 °C.

{001} Oriented piezoelectric films prepared by chemical solution deposition on Ni foils

Flexible metal foil substrates are useful in some microelectromechanical systems applications including wearable piezoelectric sensors or energy harvesters based on Pb(Zr,Ti)O3 (PZT) thin films. Full utilization of the potential of piezoelectrics on metal foils requires control of the film crystallographic texture. In this study, {001} oriented PZT thin films were grown by chemical solution deposition (CSD) on Ni foil and Si substrates. Ni foils were passivated using HfO2 grown by atomic layer deposition in order to suppress substrate oxidation during subsequent thermal treatment. To obtain the desired orientation of PZT film, strongly (100) oriented LaNiO3 films were integrated by CSD on the HfO2 coated substrates. A high level of {001} LaNiO3 and PZT film orientation were confirmed by X-ray diffraction patterns. Before poling, the low field dielectric permittivity and loss tangents of (001) oriented PZT films on Ni are near 780 and 0.04 at 1 kHz; the permittivity drops significantly on poling due to in-plane to out-of-plane domain switching. (001) oriented PZT film on Ni displayed a well-saturated hysteresis loop with a large remanent polarization ∼36 μC/cm2, while (100) oriented PZT on Si showed slanted P-E hysteresis loops with much lower remanent polarizations. The |e31,f| piezoelectric coefficient was around 10.6 C/m2 for hot-poled (001) oriented PZT film on Ni.

Phase and electrical properties of PZT thin films embedded with CuO nano-particles by a hybrid sol-gel route

Pb(Zr0.52Ti0.48)O3 or PZT thin films embedded with CuO nano-particles were successfully prepared by a hybrid sol-gel process. In this process, CuO (0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1 wt. %) nanopowder was suspended in an organometallic solution of PZT, and then coated on platinised silicon substrate using a spin-coating technique. The influence of CuO nano-particles’ dispersion on the phase of PZT thin films was investigated. XRD results showed a perovskite phase in all films. At the CuO concentration of 0.4–1 wt. %, a second phase was observed. The addition of CuO nano-particles affected the orientation of PZT thin films. The addition was also found to reduce the ferroelectric properties of PZT thin films. However, at 0.2 wt. % CuO concentration, the film exhibited good ferroelectric properties similar to those of PZT films. In addition, the fatigue retention properties of the PZT/CuO system was observed, and it showed 14% fatigue at 108 switching bipolar pulse cycles while the fatigue in PZT thin films was found to be 17% at the same switching bipolar pulse cycles.

Misfit strain dependence of ferroelectric and piezoelectric properties of clamped (001) epitaxial Pb(Zr0.52,Ti0.48)O3 thin films

A study on the effects of the residual strain in Pb(Zr0.52Ti0.48)O3 (PZT) thin films on the ferroelectric and piezoelectric properties is presented. Epitaxial (001)-oriented PZT thin film capacitors are sandwiched between SrRuO3 electrodes. The thin film stacks are grown on different substrate-buffer-layer combinations by pulsed laser deposition. Compressive or tensile strain caused by the difference in thermal expansion of the PZT film and substrate influences the ferroelectric and piezoelectric properties. All the PZT stacks show ferroelectric and piezoelectric behavior that is consistent with the theoretical model for strained thin films in the ferroelectric r-phase. We conclude that clamped (001) oriented Pb(Zr0.52Ti0.48)O3 thin films strained by the substrate always show rotation of the polarization vector.

A Study on the Piezoelectric Properties of PZT and Doped PZT Thin Films by Sol-Gel Method

This study examined the effect of crystalline orientation and dopants such as Nb and Zn on the piezoelectric coefficient of sol-gel driven Pb1(Zr0.52Ti0.48)O3(PZT) and doped PZT thin films. Crack-free 1-μm-thick PZT and doped PZT thin films prepared by using 2-Methoxyethanol-based sol-gel method were fabricated on Pt/Ti/SiO2/Si substrates. The highly (111) oriented PZT thin films of pure perovskite structure could be obtained by controlling various parameters such as a PbTiO3 seed layer and a concentration of sol-gel solution. The Nb-Zn doped PZT thin films exhibited high piezoelectric coefficient which was about 50 % higher than that of undoped PZT thin film. The highest measured piezoelectric coefficient was 240 pC/N, which could be applicable to piezoelectrically operated MEMS actuator, sensor, or energy harvester devices.

Preparation and Dielectric Properties of Oriented PZT Thin Films by LB Technique

The oriented La modified PZT thin films were prepared on Pt/Ti/SiO2/Si substrate by the LB technique. The pre-sintering temperatures and the annealing temperatures for La modified PZT were determined by TG-DTA curves and XRD detect results. XRD detection of PZT and PZT with different La amount illustrated the crystal constructions and the effects by modification. The AFM observation of PLZT thin films with organic acid indicated that the LB technique could obtain smooth and flat film with the deposition of PLZT particles within nanometers on substrate. The detection results of the electrical properties indicated that the modification of La had great influence on the electric properties of LB thin film. PLZT thin film by annealing at 650°C had better dielectric constant of 569.2 and dielectric loss of 0.4915 at 5 kHz. And the amount of La of 2% in mass gave the piezoelectric constant of 14pC/N.

Improved ferroelectric properties of Pb(Zr0.52,Ti0.48)O3 thin film on single crystal diamond using CaF2 layer

The authors report the integration of perovskite Pb(Zr0.52,Ti0.48)O3 thin film on single crystal diamond by using a nonoxide single CaF2 buffer layer. The CaF2 buffer layer plays a dual role in the lead zirconate titanate Pb(Zr,Ti)O3 (PZT) film deposition. The first is that the CaF2 layer leads to a preferentially (100)-oriented PZT thin film on diamond, improving the ferroelectric properties significantly. The PZT film exhibits a remanent in-plane polarization of 2Pr=68 μC/cm2 and a coercive field of 33 kV/cm. The remanent polarization is much larger than that of PZT films deposited on diamond by using SrTiO3/Al2O3 buffer layer. The second is that the CaF2 layer acts as an efficient energy barrier for the metal-ferroelectric-insulator-diamond capacitor due to its wide band gap. The leakage current in the capacitor is reduced to be lower than 10−6 A/cm2 in the forward bias mode.

Orientation controlling of Pb(Zr0.53Ti0.47)O3 thin films prepared on silicon substrates with the thickness of La0.5Sr0.5CoO3 electrodes

Pb(Zr0.53Ti0.47)O3 (PZT) thin films were prepared on La0.5Sr0.5CoO3 (LSCO) coated Si substrates by a sol–gel route. The thickness of LSCO electrode was found to modify the preferential orientation of PZT thin films, which consequently affected the dielectric and ferroelectric properties. (100) textured PZT films with dense columnar structure could be obtained on the top of (110) textured LSCO with thickness of 230 nm. PZT thin films prepared on the optimized LSCO films exhibit the enhanced dielectric constant and remnant polarization of 980 and 20 μC/cm2, respectively.

Structural and electrical properties of Pb(Zr 0.53Ti 0.47)O 3 films prepared on La 0.5Sr 0.5CoO 3 coated Si substrates

PbZr 0.53Ti 0.47O 3 (PZT) thin films with thickness of 0.9 μm were prepared on La 0.5Sr 0.5CoO 3 (LSCO) coated Si substrates. Both PZT and LSCO were prepared by the sol–gel method. The concentration of LSCO sol was varied from 0.3 to 0.1 mol/L, which could modify the preferential orientation of PZT thin films and consequently affect the dielectric and ferroelectric properties. The LSCO electrode layers derived from lower sol concentration of 0.1 mol/L have much more densified structure, which facilitates the formation of (1 0 0) textured PZT films with smooth and compact columnar grains. PZT thin films prepared on the optimized LSCO films exhibit the enhanced dielectric constant and remnant polarization of 980 and 20 μC/cm 2, respectively.

Highly c-Oriented PbZr[sub 0.48]Ti[sub 0.52]O[sub 3] Thin Films on Glass Substrates

We obtained preferentially (220)-oriented yttria-stabilized zirconia (YSZ) buffer layers on glass substrates by pulsed laser deposition. These preferentially (220)-oriented YSZ buffer layers enabled us to grow preferentially (100)-oriented bottom electrodes. On the preferentially (100)-oriented bottom electrodes, we obtained preferentially -oriented (PZT) thin films, which were confirmed by an X-ray diffraction experiment. The highly -oriented PZT thin films exhibited a high ferroelectric polarization of about . We also checked a high storage density of about with a minimum bit size below with the highly -oriented PZT thin films by electric force microscope.

Effect of Back-Etching on Electrical Properties of (111) - oriented PZT thin films

Effect of Back-Etching on Electrical Properties of (111) - oriented PZT thin films